Incandescent lamp containing a getter for binding water vapor



H J. H. BEUVENS ETAL 3,465,193 INCANDESCENT LAMP CONTAINING A GETTER FOR BINDING WATER VAPOR Filed Sept. 12, 1967 Sept. 2, 1969 FIGM 1N VENTOR AGE/V United States Patent 3,465,193 INCANDESCENT LAMP CONTAINING A GETTER FOR BINDING WATER VAPOR Herman Joseph Hendrik Beuvens and Jan Jacob Schuitemaker, Emmasingel, Eindhoven, Netherlands, assignors, by mesne assignments, to U.S. Philips Corporation, New York, N.Y., a corporation of Delaware Filed Sept. 12, 1967, Ser. No. 667,189 Claims priority, application Netherlands, Sept. 15, 1966, 6613009 Int. Cl. H01j 19/68, 19/70, 61/24 US. Cl. 313-178 5 Claims ABSTRACT OF THE DISCLOSURE A getter for an incandescent lamp consisting of a metal phosphide which reacts with water-vapor at room temperature but does not dissociate into metal and phosphorus at the operating temperature of the part of the lamp where it is located.

The invention relates to a getter for an incandescent lamp, particularly a getter which binds water-vapor even at ambient temperatures.

In general, both gas-filled and exhausted incandescent lamps contain small quantities of solid substances, socalled getters, which are capable of binding gases.

Getters are used either for binding residual gases in order to improve or to maintain the vacuum in the lamp (known materials for this purpose are especially phosphorus and also zirconium and barium), or for binding residual gases adversely affecting the life of the lamp, such as oxygen and water-vapor. Known getter materials for this purpose are zirconium, barium and sodium. These getters can be used both in gas-filled and in exhausted lamps, in the latter case, if desired, in conjunction with phosphorus.

Phosphorus is very frequently used in incandescent lamps. It is applied in the form of the red modification in the lamp to an area which, during operation of the lamp, assumes a temperature exceeding the evaporation temperature of red phosphorus. In general, the filament wire is chosen for this purpose. The evaporated phosphorus reacts with residual gases still present in the incandescent lamp, such as oxygen and is deposited on the wall of the bulb in the form of the yellow modification. A yellow lamp bulb which is colored by phosphorus is commercially aesthetically not acceptable. Therefore, it is customary to introduce only such quantity of phosphorus into the lamp that substantially no phosphorus can deposit on the wall of the bulb. However, this means that, although the bulb does not, or substantially does not contain any residual gases, such as oxygen, immediately after the evaporation of the red phosphorus, the water-vapor released during the life of the lamp from, for example, the bulb wall is not, or is insufficiently bound.

An object of the invention is to provide an incandescent lamp in which, beside containing any other getters for binding residual gases such as oxygen, contains a getter whichnaturally depending upon the quantity used and upon the quantity of water-vapor which is released from the bulb wall during the life of the lamp and which is present at the beginning of this life-is capable of binding water-vapor during the whole life of the lamp.

According to the invention, this is achieved with an incandescent lamp which contains as a getter a metal phospide which reacts with water-vapor already at room temperature and which is applied to an area in the lamp at which the temperature does not increase either during the manufacture or during the operation of the lamp 3,465,193 Patented Sept. 2, 1969 to or above a temperature at which the metal phosphide dissociates into metal and phosphorus.

Phosphide suitable for this purpose are the phosphides of aluminum, arsenic, barium, beryllium, calcium, lithium, magnesium, sodium and strontium.

It already has been proposed to eliminate another disadvantage with the use of phosphorus in incandescent lamps by the application of metal phosphides. When phosphorus is used in the manufacture of incandescent lamps, careless processing may result in phosphorus escaping from the lamp and arriving in vacuum pumps or at other undesired areas. This is prevented according to this proposal by applying a metal phosphide either to the filament wire, or to another area in the incandescent lamp which, during operation, assumes a temperature exceeding the dissociations temperature of the particular metal-phosphide. During the operation of the lamp, the phosphide dissociates into metal and phosphorus and the phosphorus can then bind the residual gases in the lamp, such as oxygen. This method has the same disadvantage as a method in which phosphorus itself is used, i.e., the use of an unduly large amount results in yellow-colored lamps being obtained. In this known method generally phosphides such as copper phosphide are applied which do not react with water at room temperature.

The phosphides used in the incandescent lamp according to the invention are preferably the phosphides of aluminum, .arsenic or magnesium. These phosphides react less strongly with water-vapor at room temperature than the other aforesaid phosphides of the alkali and alkaline earth metals, but their reaction is sufficiently rapidly for the intended purpose. It has been found in practice that aluminum phosphide can be most readily manufactured and handled.

In order to prevent the phosphide for reacting with water-vapor from the ambient atmosphere already before its application in the lamp, in which process the toxic phosphine gas (PH) is formed, according to a further aspect of the invention, the metal phosphide reactive with water vapor is introduced into the lamp in the form of grains surrounded by a film of synthetic resin which can be removed thermally without the formation of carbon. These grains are applied to an area which during the exhaustion of the lamp assumes, or is heated, to a temperature such that the film of synthetic resin evaporates completely, if desired, while it is depolymerized. The vapors then developed are evacuated from the lamp. The temperature at which the vapors are removed is naturally not allowed to exceed the temeprature at which the metal phosphide starts dissociating.

A synthetic resin suitable for this purpose is polymethylmethacrylate, the evaporation temperature of which is approximately 350 C.

The invention will now be described more fully with reference to the accompanying drawing in which,

FIG. 1 is a sectional view of a mount of an incandescent lamp according to the invention to which a getter is applied, and

FIG. 2 is .a sectional view of an incandescent lamp after mount and bulb have been fused together.

The mount of FIGURE 1 comprises inter alia a stem tube 1 and a flange 2. The stem tube 1 accommodates an exhaust tube 3 which emerges at the pinch 4. The mount is further provided in the usual manner with a with a filament wire 5 and with current-supply conductors 6 and 7.

A small quantity of a metal phosphide suspension consisting, for example, of 20 gms. of aluminum phosphide, mls. of xylene and 8 gms. of polymethacrylate is applied at 8 by means of a brush or by other suitable means.

Subsequently, the mount is sealed into a bulb 9 which is exhausted through the exhaust tube 3. The temperature then increases at 8 to approximately 400 C. and the polymethacryate dissociates.

The use of a getter of metal phosphide according to the invention results in a life which, in the case of 25 watt exhausted lamps, may be approximately 200 hours longer than that of lamps in which such a getter is not used.

While the invention has been described in connection with a particular embodiment thereof, other modifications will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In an electric incandescent lamp, a getter consisting of a metal phosphide which reacts with water-vapor at room temperature, said getter being applied to an area in the lamp at which the temperature does not increase during the manufacture and operation of the lamp to a temperature at which the metal phosphide dissociates into metal and phosphorus.

2. A getter for an elecetrie incandescent lamp as claimed in claim 1 consisting of a phosphide of a metal selected from the group consisting of aluminum, arsenic, and magnesium.

UNITED STATES PATENTS 1,249,978 12/1917 MacKay 3l3174 X 1,989,790 2/1935 Dietz 252-18l.6 2,393,584 1/1946 Bennett 3l3-174 2,491,880 12/1949 Van Liempt 313174 JAMES W. LAWRENCE, Primary Examiner RAYMOND F. HOSSFELD, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,465,193

Dated September 2 1969 Inventofls) Herman J.H. Beuvens: Jan J. Schuitemaker It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 39, (PH) should be (PH Column 2, line 50,

"temeprature" should be -temperature Signed and sealed this 23rd Edward M. Fietchm', 3n.

Anesting Officer day of June 1970.

SIGNED A'ND SEALED JUN231970 WILLIAM E. Sam, 38.. Commissioner of Patents 

